For wireless communication, a diplexer can help process signals carried in a carrier aggregation system. In carrier aggregation systems, signals are communicated with both high band and low band frequencies. In a chipset, the diplexer is usually inserted between an antenna and a tuner (or a radio frequency (RF) switch) to ensure high performance. Usually, a diplexer design includes inductors and capacitors. Diplexers can attain high performance by using inductors and capacitors that have a high quality (Q)-factor. Higher performance of diplexers can also be attained by reducing the electromagnetic coupling between components, which may be achieved through an arrangement of the geometry and direction of the components. Diplexer performance may be quantified by measuring the insertion loss and rejection (e.g., quantities expressed in decibels (dB)) at certain frequencies.
The diplexer fabrication process may be compatible with standard semiconductor processes, such as processes for fabricating voltage-controlled capacitors (varactors), switched-array capacitors, or other like capacitors. It may be beneficial to fabricate the components of the diplexer design on a single substrate. Fabrication on a single substrate may also enable tunable diplexers that are tuned through a variety of different parameters.
Fabricating high performance diplexers in an efficient and cost-effective manner is problematic. Increasing the Q-factor of the inductors and the capacitors in the diplexer is also an issue. Reducing the electromagnetic coupling between the various components in the diplexer, while decreasing the size of the diplexer and making the most economical use of resources, would be beneficial.